1. Field of the Invention
This invention is directed (1) to improving the properties of coals and in particular to converting a moderately, weakly or non-caking coal into a highly caking coal and (2) to improving the properties of coal liquids and gases which are produced during the coke formation. This invention is also directed to improving the quality and increasing the quantity of solvent-extracted coal liquids.
2. Description of the Prior Art
Formation of coke from moderately, weakly or non-caking coals usually involves the physical mixing or blending of a binder material into the coal prior to pyrolysis to increase or produce caking properties. This material helps to agglomerate the coal into a molten plastic or liquid state when it is heated. Subsequently, when the coke is cooled, a coherent solid is formed which by appearance is isotropic and has a hardness which is suitable for metallurgical processes.
Coal fines and coal dust, as well as non-caking and weakly caking coals, have been variously treated, such as by adding binders, to improve caking properties. Examples of binders employed in the prior art are coal-derived or petroleum derived carbonaceous materials such as coal extracts, tar, pitch, tar oil, fuel oil, asphalt, crude petroleum extracts, bitumen and the like. However, large amounts of any binder are usually required in order to form a caking coal. Even when only small amounts of additives are required (e.g., solvent-refined coal - see U.S. Pat. No. 2,686,152), they are usually very expensive.
Coal liquids and gases derived from pyrolysis of the coal evidence generally undesirable properties. Coal liquids are unstable and tend to polymerize in a matter of days to form highly viscous liquids and eventually solid tars. Coal gases evidence low heat contents.